Seismic S waves, also known as shear or secondary waves, travel through solids. They are not able to propagate through liquids or gases because they require a medium with particles that can move past one another, which is a characteristic of solid materials. S waves are slower than P waves (primary waves) and are缺席 (absent) in liquids and gases due to the lack of this particle movement capability. read more >>

Both types of seismic wave can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth. This is because P-waves can travel through solids and liquids whereas S-waves can only travel through solids. This means the liquid part of the core blocks the passage of S-waves.read more >>